Propulsion means



R. D. SCHULTZ ETAL 3,122,882

March 3, 1964 PROPULSION MEANS 5 Sheets-Sheet 2 Filed Nov. 25. 1960 rJnEDw QO IOU 023016 zmhzuz 0... mm;

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PROPULSION MEANS 5 Sheets-Sheet 4 Filed Nov. 23. 1960 Ill INVENTOR. SCHULTZ BRANSON BY ROBERT F. CHAIKEN LANE K.

ATTORNEY March 3 1964 R. D. SCHULTZ ETAL 3,122,882

PROPULSION MEANS 5 Sheets-Sheet 5 Filed Nov. 23, 1960 IN V EN TOR.

ROBERT D scHuu'z LANE K. mmsou ROBERT F. CHAIKEN ATTORNEY United States Patent ration of Ohio Filed Nov. 23, 1960, Ser. No. 71,329 23 Claims. (Cl. Gil-35.5)

This invention relates to a system for creating thrust under conditions of substantial vacuum generally, and to a system for propelling vehicles in outer space in particular.

Heretofore, a common method of creating thrust for purposes of propelling rockets or the like has involved the rapid creation of gases under pressure in a thrust chamher by burning chemical fuels therein. While this has proven the most common method used to obtain sufficient thrust for the propulsion of rockets within the earth's atmosphere and gravitational field, there are a number of disadvantages to the use of chemical fuels in outer space. Among them are the difi'iculty of carrying an adequate supply of fuel and oxidizer from earth and, when liquid propellants are used, the inherent danger of malfunction due to the unavoidably complex nature of liquid chemical propellant systems. a

We have found that a jet of highly charged colloidalsized droplets can be formed under vacuum from a liquid of suitable vapor pressure by subjecting a confined body of the liquid to a relatively large difference of electrical potential, said liquid being physically confined in a container having minute openings in the confining boundary. Hereinafter, a colloid shall be understood to mean a substnace in a state of fine division wherein its constituent particles range in diameter from about 0.2 to about 0.005 micron. By having such openings in the form of capillary tubes pointed at the outer ends, or arranging members having sharp edges or points in contiguity with the minute openings, it is found that the liquid will slowly migrate through the holes to the pointed ends of the capillary tubes or sharp edges or points of the contiguous members from whence it is ejected as charged atomized droplets of colloidal dimensions. By proper design and arrangement of the openings and capillary tubes or sharp edges or points, the streams of atomized and charged liquid droplets may be so positioned and distributed that they may be readily focused and accelerated to produce thrust in a given direction.

It is therefore the principal object of the present invention to provide a novel method of and improved means for reaction-propulsion of a space flight vehicle.

Another object of the present invention is to provide a novel method of and improved means for vernier control of the orbit of a military-communication, reconnaissance, or metreological-observation satellite.

In its principal aspect the invention comprises a unique pro ulsion unit 0 erab substantial vacuum w erein colloidal size electrically charged iqui particles or droplets are ejected from points in contiguity with the liquid container. The charged particles are focused and accelerated through a gradient electrostatic field to produce thrust in a given direction. The charged particles may be directed to the ejection points through capillary tubes, or members in contiguity with the container having sharp edges or projections, or a combination of both may be employed.

These and other objects, aspects and features of this invention will be apparent to those skilled in the art from the following more detailed description taken together with the appended drawings wherein like or similar elements are afforded prime designations, and:

FIG. 1 shows a cross-sectional view of one embodiment 3,122,882 Patented Mar. 3, 1964 of a propulsion unit according to this invention, together with a block and schematic diagram of the novel system in which it is incorporated;

FIG. 2 is a sectional view in detail of the propulsion unit of FIG. 1;

FIG. 3 is a plan view of the needle spray bank of the propulsion unit taken along section line 33 of FIG. 2;

FIG. 4 shows a sectional view of another embodiment of the propulsive unit of this invention which utilizes capillary tubes as a means for effecting escape of a liquid from confinement as charged atomized droplets;

FIG. 5 is a plan view of the capillary spray bank of the propulsion unit of FIG. 4 taken along section line 5-5 thereof;

FIG. 6 shows in section a combination needle-capillary tube spray bank which may be utilized in the propulsion unit of FIG. 1, together with an alternate means of neutralizing space charge tending to disrupt the colloid beam;

FIG. 7 illustrates a plan view of an alternate spray bank assembly in the form of a knife edge;

FIG. 8 shows a section view of the knife edge spray bank assembly taken along section line 8-8 of FIG. 7;

FIG. 9 discloses in a plan view yet another spray bank assembly in the form of a spiralknife edge for use in the propulsion unit of FIG. 1; and

FIG. 10 shows a section view of the spiral knife edge spray bank taken along section line 1010 of FIG. 9.

The novel propulsion unit of the present invention embodied in a space propulsion system is illustrated in FIG. 1. High voltage electrical energy, necessary for the operation of the propulsion unit, is furnished by a high voltage generator 10, shown to be driven from a closed turbine cycle. A nuclear reactor 12 heats working fluid which is directed to and expanded within a turbine 14. The fluid exhaust from the turbine is cooled in a radiator 16, the waste heat being directed to the ambient, and the cooled fluid then compressed in compressor 18 and fed back to the reactor 12 for reheating. The rotation of the turbine 14 drives the generator 10 thereby generating the electric power necessary for the operation of the propulsion unit. The closed-cycle thermal power plant described is not an absolute requirement of the present invention. The gen erator 10 could be driven by other means, such as by a turbine actuated by rocket exhaust gases. However, for true space flight it is contemplated that a solar or nuclear power source will be utilized, a thermonuclear source being preferable for extremely high power levels. The high I voltage generator may be, preferably, an elecirostatic generator capable of supplying an extremely high voltage and low current output, and may be of any type known to those skilled in the art such as, for exarnple, a Van de Graaii generator.

The output lead 20, 22 of the generator 10 are connected to the novel propulsion unit 24 of the present invention. A first lead 20 is connected to the positive terminal of the generator whereas the second power lead 22 is connected to the negative terminal of the generator, both leads being connected at their other end to the propulsion unit 24, as will be later shown.

The propulsion unit itself 24 comprises a spray bank 26 and associated apparatus. Te spray bank 26 comprises a chamber or container 32 in which the propulsive liquid 34 is confined. This liquid is subjected to a high positive voltage by means of a circular electrode 36 which encompasses the container 32 and is connected to the first or positive power lead 20. Openings 23 on one face of the confining chamber 32 are provided through which the liquid migrates under the influence of a force such as applied pressure or capillary attraction. The various types of spray banks and their associated components used by thte propulsion unit of this invention are shown in more detail in succeeding Figures. A drift tube assembly 38 is arranged adjacent the discharge openings 28 of the confined chamber 34. The assembly 38 comprises drift tubes or accelerating rings spaced in a manner surrounding the proposed path of the charged colloidal droplet 40. The drift tube 42 furthest in distance from the spray bank 26 is connected to the negative power lead 22 of the electrostatic generator 10. The drift tube 30 closest to the spray bank 26 is connected to the positive power lead 20 of the generator 10 through a portion 44 of the voltage divider 47. It is seen that the potential gradient between the fluid 34 in the spray bank assembly 26 and the furthest drift tube 42 is provided by the presence of a voltage divider 47, the individual drift tubes achieving their potential from voltage taps intermediate the length of the voltage divider 47. By this arrangement, an electric field is provided which has a potential gradient varying from a positive value at the spray bank 26, neutral at the first drift tube 30, to a high negative value at the furthest drift tube 42. Adjacent the rearmost accelerating ring 42 is arranged a shield member 46 within which is located an electron or negative ion emitter 48. The shield 46 is connected to be at the same high negative potential as the furthest ring 42, and the emitter 48 is powered by a separate voltage source, not shown. It is the function of the emitter 48 to inject negative particles into the beam 40 of colloidal droplets to overcome the space-charge repulsion phenomena, while the shield 46 insures that the negative particles are confined to the vicinity of the beam 40.

FIG. 2 shows in more detail a sectional view of the novel propulsion unit 24 of the present invention having a needle spray bank assembly. This unit provides a beam of charged colloidal particles 40 having a net positiive or negative charge, depending upon the polarization of the exciting voltage. The beam has a large cross-section and may be modified to any desirable configuration. Operation for sustained length of time is possible because of the fluid reservoir feature and mechanism for supplying additional fluid to the reservoir from a larger supply may be provided. Pulsed operation is also possible.

The needle spray bank assembly 26 comprises a first plate 50 to which are attached steel pins 52 of a small diameter, for example, in the neighborhood of .030 inch. The pins protrude through a similar pattern of holes 28' which have a diameter of approximately .003 inch greater than the diameter of the pins, the holes being in a second plate 54. Between the two plates 50, 54 is provided a reservoir for the fluid 34' to be dispensed. The rounded configuration of the high voltage electrode 36 is provided to prevent high voltage leakage from the sharp corners of the plate 50, 54. FIG. 3 shows a plan view of r the needle spray bank giving full details of its construction. A high positive voltage (for positively charged colloids), as shown here, or a high negative voltage (for negatively charged colloids) is applied to the high voltage electrode 36. This high voltage is transmitted to the points of the pins 52 and a spray 40' of charged particles is produced. The fluid 34' flows from the reservoir down the pins 52, maintaining the spray 40'. This flow is produced by gravity and capillary action, but could be produced by pressurizing the fluid 34 in the reservoir, in the absence of a high gravitational field. A spacer 56 is provided between the plates 50, 54 to provide the proper chamber rigidity. An accelerating field for the colloid beam 40 is provided by the drift tube assembly 38 which is energized by the generator, the potential on each ring and the spray bank electrode 36' being determined by taps off the voltage divider 47.

FIGS. 4 and illustrate a capillary spray bank propulsion unit 26" identical to that of FIGS. 2 and 3 with the exception that the liquid 34" is caused to migrate through openings which are preferably capillary tubes 58 pointed at the outer ends and arranged in banks to yield colloid beam 40" comprising a plurality of properly spaced streams of colloidal droplets. The liquid 34" passes through the tubes 58 under the force of capillary attraction and is atomized from the pointed outer ends thereof. The reason for the atomization and dispersal of the liquid from the capillary tips as described can be attributed to the large electrostatic pressure developed by the repulsion of like charges at the surface of the liquid 34", and also to a partial electrical breakdown of the liquid subjected to the high electrostatic field at the capillary tip. By way of further explanation, when this electrostatic pressure exceeds the tensile strength of the liquid at the capillary tip, the liquid flies apart and forms the charged colloidal droplets.

In operation, the apparatus of our invention functions as follows: high voltage is supplied from a convenient source such as the electrostatic generator 10 and the voltage of positive polarity is applied to the liquid propellant material 34. The liquid under high voltages migrates to the points of the needles 52 (FIGS. 2 and 3), or the ends of the capillary tubes 58 (FIGS. 4 and 5), from whence it is atomized as charged colloidal droplets. These droplets are immediately subjected to an electrostatic field of increasingly greater negative potential created by the drift tube assembly 38. The electrostatic field focuses and accelerates the charged particles of the colloid beam 40 so that they travel along a fixed path at an accelerating rate to some predetermined exhaust velocity. The negative particles ejected by the emitter 48 into the colloid beam 40 as it emerges from the endmost drift tube ring 42 neutralize space-charge phenomena tending to attenuate the thrust produced by the beam. We have found that potential radiation from about kilovolts at the spray bank electrode 36 to about -l000 kilovolts at the furthest drift tube 42 to be particularly suitable for the purposes of our novel propulsion system, although other voltage ranges may be employed.

Reference is made to FIG. 6 which shows in section a propulsion unit utilizing a combination needle-capillary tube spray bank which may be employed with the propulsion system of FIG. 1. An additional feature of this embodiment is a novel method of and means for neutralizing space charge tending to disrupt the colloid beam by passing the charged colloid beam through a rarefied neutral gas. As seen from the figure, the spray assembly 26" is a composite of the assemblies disclosed in the previous figures. Needles 52' protrude through the hole openings at the end of capillary tubes 58'. The spray bank assembly is similar in all other respects, and is utilized in conjunction with a drift tube assembly 38 energized in any manner previously described. Adjacent the rearmost accelerating ring 42" is arranged the improved neutralization means permitting passing the charged colloid beam 40 through a rarefied neutral gas 60 in a manner that corona discharge induced by voltage gradients on the charged colloidal particles occurs in the gas 60. The electric charge on the rapidly moving colloidal droplets is thus transferred to the slower moving gas without materially effecting the velocity, hence thrust, of the colloidal particles in the beam 40'. To achieve this space charge neutralization, liquid capable of vaporization upon application of heat is arranged in a storage tank 62. Heat is applied to the tank, as from the reactor 12 of FIG. 1 for example, and the resulting vapor is moved by a pump 64 to a discharge nozzle 66 in the vicinity of the furthest drift tube assembly ring 42". The gas 60 is discharged from the nozzle 66 into the charged colloid beam 40. The charges from the colloidal droplets are transferred to the gas particles, the gas particles being directed to gas receiving means 68 where they are channeled into condenser 70 and condensed to the liquid state and returned to the storage tank 62, where the liquid is heated to repeat the cycle. The entire neutralization system is preferably kept at neutral or ground potential, as shown at point 72. An ideal neutral gas is the material used in the colloid beam, for example, a low vapor pressure fusion pump oil such as dioctylphthalate. Removing the charge of the colloidal beam at the time ejection from the carrying vehicle is considered beneficial as image forces from the vehicle carrying the apparatus may render the colloidal stream ineifectua'l by either confining the stream to the vicinity of' the vehicle or preventing the injection of further particles, thereby considerably attenuating the thrust from the unit.

FIGS. 7 and 8 show an alternate spray bank assembly in the form of a knife edge which may be used in the propulsion system of FIG. 1. As seen from the figures liquid is allowed to flow from the reservoir through minute slits 80 in one wall 82 of the assembly on to the knife edges 84 where it is discharged in the form of charged colloidal size droplets as previously explained.

FIGS. 9 and 10 show a variation of the knife edge spray bank wherein the ejection member 94 is in the form of a continuous spiral. The spiral plate 94 is secured to the outer face of one wall 92 and the liquid flows from the reservoir to the plate through a continuous minute slit 90 which is contiguous to the plate 94 and is also spiral in form.

The spray bank units shown in FIGS. 7-10 are similar in other respects to those disclosed in the previous figures, their distinction lying in the use of a sharp edge instead of a point to produce the high field gradient necessary to produce dispersion of the colloidal droplets.

The propulsive system of this invention is particularly useful for purposes of maneuvering vehicles, artificial satellites, and the like in space. For purposes of changing the direction of objects such as space vehicles substantially outside of the earths enveloping atmosphere and sphere of strong gravitational force, a very small amount of thrust will sufiice. A charged colloidal jet from our novel system is amply snfiicient to supply the necessary amount of thrust for such purposes.

Although various liquids have been subjected to atomization in the past, such experiments have always been carried out at atmospheric pressure or, at any rate, at some pressure substantially above a vacuum. The essence of the present invention is our discovery that by means of the system described herein electrical atomization can be carried out at high vacuum or in an atmosphere in which the residual gas pressure is approximately 10- to 10- mm. Hg or less. Since high vacuum exists in space at altitudes greater than 190 kilometers, our propulsion system is particularly suitable for the propulsion of objects in outer space.

Liquids suitable for use as propellants in our charged colloid propulsion system are those having a vapor pressure of 10' mm. Hg or lower at 20 C. Use of a liquid having a low vapor pressure is important in practicing the present invention in order to prevent charge leakage from the colloidal particles by corona discharge. In addition, it is desirable, although not absolutely necessary, that the liquids have the following properties: an internal pressure greater than about 7 l0 dynes per square centimeter; electrical conductivity greater than 6 l0* mho/cm. but less than about 10* mho/cm.; a dielectric constant greater than 6; a density of about 1 to 1 /2 grams/cm A freezing point as low as possible, consistent with the above properties is also desirable. A liquid which we have found to be particularly suitable as a propellant for our novel system is dioctylphthalate, available commercially under the trade name of Octoil as a product of Consolidated Electrodynamics Corporation. Other suitable liquids are polypropylene-glycol, or glycerine.

Although it is preferred that the propulsive liquid be subjected to a high positive potential in the operation of our novel propulsion system, it is not essential that this be the case. The important factor is that there be a large potential difference between the charged colloidal droplets and the gradient electrostatic field through which they travel. Thus, it is within the scope of our invention to impress a high negative voltage on the liquid and accelerate the resulting charged particles through a gradient electrostatic field becoming more positive in potential.

It is also within the scope of the invention to maintain the points of emission of the atomized droplets at ground potential while maintaining the accelerating units (grids or drift tubes) at high negative or positive voltage.

While we have illustrated and described many details of construction, alternatives and equivalents will occur to those skilled in the art which are within the scope and spirit of our invention; hence it is our desire that our protection be not limited to the details herein illustrated and described, but only by the proper scope of the appended claims.

We claim:

1. A reaction propulsion system for producing thrust in a substantial vacuum comprising: a body of liquid having a vapor pressure not greater than 10* mm. Hg at about 20 cent-igrade; means for confining said body of liquid, said confining means having minute openings in a portion of a surface thereof, through which the liquid may migrate; liquid dispersion means in contiguity with said minute openings; means for subjecting said confined liquid to a relatively high electric potential; means for creating and maintaining a gradient electrostatic field in a spaced relationship to said dispersion means, whereby charged droplets of the liquid are ejected from said dispersion means as the result of said high potential .and are focused and accelerated in any desired direction, and means for injecting negative particles into said droplets after they have been focused and accelerated.

2. The reaction-propulsion system of claim 1 wherein said liquid is dioctyl phthalate.

3. The reaction-propulsion system of claim 1 wherein said liquid is polypropylene glycol.

4. The reaction-propulsion system of claim 1 wherein said liquid is glycerine.

5. The reaction-propulsion system of claim 1 wherein said dispersion means comprises capillary tubes.

6. The reaction-propulsion system of claim 1 wherein said dispersion means comprise a plurality of electrically conductive members having sharp projections which are arranged to project to the ambient through the minute openings in said surface of said confining means.

7. The reaction propulsion system of claim 1 wherein said dispersion means comprises a thin metallic plate having a thin edge.

8. The reaction propulsion system of claim 1 wherein said dispersion means comprises a thin metallic plate which is volute in form.

9. The reaction propulsion system of claim 1 wherein said dispersion means comprises a plurality of capillary tubes, each of which has an electrically conductive needlelike member centrally located therein.

10. The reaction-propulsion system of claim 1 wherein said high potential means furnishes approximately kilovolts of one polarity and said means for creating and maintaining a gradient electrostatic field creates a field which varies from zero potential in the vicinity of said ejection means to a maximum potential of approximately 1,000 kilovolts of an opposite polarity at the point where the charged colloid beam leaves the propulsion system.

11. The reaction-propulsion system of claim 1 wherein said liquid has an electrical conductivity greater than 6X10 mho/cm., but less than about 10- mho/cm.

12. A reaction-propulsion system as described in claim 11 wherein said liquid has a dielectric constant greater than 6.

13. A reaction-propulsion system as in claim 12 wherein said liquid is of a density of about 1 to 1 and V2 g./cm.

14. A reaction-propulsion system as in claim 13 wherein said liquid has an internal pressure greater than 7 X 10 dynes per square centimeter.

15. A propulsion system operable in a vacuum atmosphere comprising: a reservoir having a plurality of openings in a portion of a surface thereof; a body of liquid having a vapor pressure not greater than 10- mm.

Hg at about 20 Centigrade arranged in said reservoir; fluid ejection means associated with said openings in said surface; means for applying electric potential to said fluid body in said reservoir; and electric focusing and accelerating means arranged in contiguity to said fluid ejection means.

16. A propulsion system as described in claim 15, and in addition, means for space charge neutralization, said neutralization means being associated with said focusing and acceleration means.

17. A system for creating thrust in a vacuum atmosphere comprising: a reservoir having a plurality of openings in a portion of a surface thereof; a body of liquid having a vapor pressure not greater than 10" mm. Hg at about 20 centigrade arranged in said reservoir; fluid ejection means associated with said openings in said surface; electrostatic focusing and accelerating means arranged in contiguity to said fluid ejection means; means for applying electric potential to said liquid body through said reservoir and said electrostatic focusing and accelerating means, a difference of potential existing between said reservoir and said electrostatic focusing and accelerating means whereby liquid particles of colloid size are ejected from said particle ejection means in a beam and said beam is focused and accelerated by said electrostatic focusing and accelerating means; and means associated with said electrostatic focusing and accelerating means for neutralizing the effect of space charge on said beam of particles.

18. A propulsion system as described in claim 17 wherein said neutralizing means comprises a negative particle emission source.

19. A propulsion system as described in claim 17 wherein said neutralizing means comprises a rarified neutral gas stream.

20. A propulsion system operable in a vacuum atmosphere comprising: a reservoir having a plurality of openings in a portion of a surface thereof; a body of liquid in said reservoir, said liquid having a vapor pressure not greater than mm. Hg at about centigrade, an internal pressure greater than about 7x10 dynes per square centimeter, an electric conductivity sub stantially between 6X 10- and 10- mho/cm., a dielectric constant greater than 6, and a density substantially between 1 and 1 /2 grams/cm. fluid ejection means associated with said openings in said surface; electrostatic focusing and accelerating means in spaced relation with said fluid ejection means; means for applying electric potential to said liquid body, said reservoir and said focusing and accelerating means, whereby the liquid body and reservoir are at a potential of approximately kilovolts of one polarity and a gradient electric field is created which varies from zero in the vicinity of said ejection means to approximately 1000 kilovolts of an opposite polarity at the position of said focusing and accelerating means furthest extended from said fluid ejection means; and means associated with said focusing and accelerating means for neutralizing the effect of space charge, said neutralization means being juxtaposedwith said focusing and accelerating means which is at a potential of approximately 1,000 kilovolts.

21. A method of creating thrust in a vacuum atmosphere comprising the steps of applying an electrical potential to a body of liquid having a vapor pressure not greater than 10* mm. Hg at about 20 centigrade which is confined in a means having minute openings in a portion of a surface thereof; directing said liquid to the extremities of dispersion means associated with said openings, whereby liquid particles of colloidal size and bearing an electric charge will be formed at said dispersion means extremities; ejecting said particles from said dispersion means in a beam; focusing and accelerating said beam particles; and, neutralizing the effect of space charge on said beam of particles.

22. A propulsion system operable in a vacuum atmosphere comprising: means for ejecting in a stream electrically charged atomized liquid droplets of colloidal dimensions, and electric focusing and acceleration means arranged in contiguity to said colloidal-sized fluid particle ejection means.

23. A device as described in claim 22 and, in addition, means for neutralizing the effect of space charge on said colloidal-sized fluid particle stream, said neutralizing means being associated with said electric focusing and acceleration means.

Reactors in Flight, Engineering, Feb. 28, 1958, vol. 185, No. 4799, pp. 268-270.

Nuclear Ion Rocket, SAE Journal, July 1959, vol. 67, pp. 40-42. 

22. A PROPULSION SYSTEM OPERABLE IN A VACUUM ATMOSPHERE COMPRISING: MEANS FOR EJECTING IN A STREAM ELECTRICALLY CHARGED ATOMIZED LIQUID DROPLETS OF COLLOIDAL DIMENSIONS, AND ELECTRIC FOCUSING AND ACCELERATION MEANS 